Orthodontic instrument for measuring the frankfort-mandibular plane angle



July 12, 1949., 0.1 JAMIESON 294759705 ORTHODONTIC INSTRUMENT FOR MEASURING THE FRANKFURT-MANDIBULAR PLANE ANGLE Filed Feb. 10, 1948 2 Sheets-Sheet 1 INVENTOR. flea/64 45 fJ4M/E50A/ July 12, 1949. D. J. JAMIESON ORTHODONTIC INSTRUMENT FOR MEASURING THE FRANKFORT-MANDIBULAR PLANE ANGLE 2 Sheets-Sheet 2 Filed Feb. 10, 1948 mmvroa. fiouazAs JJ JM IESO/V ATTORNEY Patented July 12, 1949 ORTHODONTIC INSTRUMENT FOR MEAS- URING THE FRANKFORT-MANDIBULAR PLANE ANGLE Douglas J. Jamieson, Detroit, Mich.

Application February 10, 1948, Serial No. 7,419

1 Claim. 1

This invention relates to an orthodontic instrument and in particular to a device for measuring the Frankfort-mandibular plane angle and the incisor-mandibular plane angle.

In orthodontics, the science of the correction of irregularities of the teeth and malformations of the jaws, the ascertainment of the Frankfortmandibular plane angle and the incisor-mandibular plane angle has proven extremely advantageous in prognosis based on research and studies of both normal and abnormal facial growth patterns.

The Frankfort-mandibular plane angle is the angle between the Frankfort plane and the mandibular plane. The Frankfort plane is a line intersecting the upper edge of the porion and the orbitale, the porion being the ear aperture, and the orbitale being a point directly below the pupil of the eye, when looking forward, located on the ridge of the bone of the eye socket. The mandible is the lower jaw bone. The mandibular plane is a line paralleling the lower border of the mandible.

The Frankfort-mandibular plane angle is not only a useful measurement in prognosis but is employed as a check on treatment for correcting malformations and the improvement of facial growth pattern and facial esthetics, and in pIOS- 'thetics.

In prosthetics, the establishment of vertical height, or the height the dentures have to be from the jawbones to establish facial harmony is very important. By using this invention, the Frankfort-mandibular angle at the best jaw position for facial esthetics can be ascertained. Then, the dentures can be constructed and checked back with the instrument, obviating all guesswork in getting a duplication of the original reading.

The incisor-mandibular plane angle is the angle of the lower anterior teeth with respect to the mandibular plane, usually read in degrees plus or minus from a line perpendicular to the mandibular plane.

The incisor-mandibular plane angle is used in determining the extent of variation of mandibular incisors from normal dentitions and to check occlusion when both the upper and lower jaws are closed or during excursive movements of the mandible, and in prosthetics.

Th Frankfort-mandibular plane angle and the incisor-mandibular plane angle are generally obtained by use of a craniostat or head spanner, or by measurement of casts of the face or jaws, photographs and head X-rays, or by other complicated scientific instruments and procedures.

These devices are not only expensive and their use time-consuming, but their use often frightens young orthodontic patients.

With the foregoing in view, the primar object of this invention is to provide an orthodontic instrument for measuring the Frankfort-mandibular plane angle and the incisor mandibular plane angle which is inexpensive and therefore available for use by all orthodontic practitioners and students, which is easily and readily manipulated, which may, be used without the aid of an assistant, which gives immediate and accurate readings, and which provides visual assurance of proper positioning when in use.

Other objects of the invention will become apparent by reference to the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a side elevational view of an orthodontic instrument embodying the invention shown with its Frankfort-mandibular plane angle delineating arm and its incisor-mandibular plane angle pointer in their normal or zero position.

Fig. 2 is a side elevational view similar to Fig. 1 except the orthodontic instrument has been used and the Frankfort-mandibular plane angle delineating arm and the incisor-mandibular plane angle pointer are positioned forreading.

Fig. 3 is a top plan view of the orthodontic instrument disclosed in Figs. 1 and 2 with dot and dash lines indicating that the Frankfort-mandibular plane angle delineating arm is bendable to aid in establishing the Frankfort plane when the instrument is in use.

Fig. 4 is a view in perspective showin an orthodontic instrument embodying the invention in use in establishing the Frankfort-mandibular plane angle and the incisor-mandibular plane angle of a patient.

Fig. 5 is an end elevational view of the orthodontic instrument disclosed in Figs. 1, 2 and 3 taken from the front end thereof.

Fig. 6 is a fragmentary sectional view taken on the line 6-6 of Fig. 1.

Fig. 7 is a fragmentary elevational view taken on the line l! of Fig. 5 opposite the incisormandible plane angle indicator.

Referring now to the drawings where like numerals refer to like and corresponding parts throughout the several views, the orthodontic instrument disclosed for the purpose of illustrating the invention comprises, in general, a mandible contact plate l0 formed to be placed conveniently in contact longitudinally with the lower border of the mandible, an upright longitudinal flange I I preferably formed integral with the forward portion of the mandible contact plate ill to rest against the side of the mandible by means of which the instrument is steadied during use, a depending longitudinal flange I2 preferably formed integral with the rearward portion of the mandible contact plate [0, a protractor l3 preferably readable to at least 50 degrees disposed normal to and above the said mandible contact plate Ii having its zero degree base line coincidental with the top of the said mandible contact plate ID, the said protractor l3 being secured to the said depending flange I2 of the mandible contact plate II] by such means as the rivets I l, a protractor or Frankfortmandibular plane angle delineating arm l5 flexible in a direction normal to the protractor l3 pivoted to the said protractor I3 on its zero degree base line rearward of the mandible contact plate It by means of a pivot pin I6 having a spring Washer [6i] disposed thereon and a thumb set screw I'I threaded thereon, to hold and fix the said Frankfort-mandibular plane angle delineating arm l5 in the desired position, and an incisor-mandibular plane angle indicator I8 pivoted on a pivot pin I9 extending through a tab 28 formed downwardly from the mandible contact plate Ill readable on a protractor scale 2| inscribed on the forward end of the flange ll of the mandible contact plate Ill preferably indicating plus or minus 30 degrees either side of a line normal to and extending upwardly from the top of the said mandible contact plate l0, and a spring washer I90 disposed on and a thumb screw 22 threaded on the said pivot pin IQ for holding and fixing the indicator IS in the desired position.

Obviously, orthodontic instruments embodying the invention may be provided with or without the incisor-mandibular plane angle indicator thereon.

In using orthodontic instruments embodying the invention, the thumb screws I1 and 22 are loosened slightly, a mark indicated by the X designated by the numeral 25 in Fig. 4 is placed on the face of the patient 30 at the orbitale and the mandible contact plate I is placed against the lower border of the patients mandible, the Frankfort-mandibular indicator arm I is pivoted from its zero position and bent over the orbitale mark, and the mandible contact plate I0 is moved along the lower border of the mandible until the lower edge of the indicator arm I5 is aligned with the said mark X at the orbitale designated by the numeral 25 and the upper edge of the porion 26 of the ear 2'! of the patient 30. In this position of the Frankfort-mandibular indicator arm I5 the thumb screw I1 is tightened. If the incisor-mandibular plane angle is also desired, the indicator I8 is pivoted until it is parallel to the mandibular incisors, and then the thumb screw 22 is tightened. The orthodontic 4 instrument is then removed from its position against the patients mandible, and the scales are read. In the example given in Fig. 4, the Frankfort-mandibular plane angle is 43 degrees, and the incisor-mandibular plane angle is minus 18 degrees.

The combination of the mandible contact plate it and the upwardly disposed flange Il makes the establishment of the mandible plane relatively a simple matter, and, the employment of a flexible Frankfort-mandibular plane angle delineator arm IE on the protractor I3 makes the Frankfort plane readily ascertainable. When the Frankfort plane and the mandible plane are established simultaneously by manipulation of the instrument, the Frankfort-mandibular plane angle is automatically established on the protractor I3. The simplicity of operation of orthodontic instruments embodying the invention has proven to be of great aid and a considerable time saver to Orthodontists and others who require Frankfort-mandibular plane angle and incisormandibular plane angle readings.

Although but a single embodiment of the invention has been disclosed and described in detail, it is obvious that many changes may be made in the size, shape, arrangement and detail of the various elements of the invention without departing from the spirit and scope thereof as defined by the appended claim.

I claim:

An orthodontic and-prosthetic instrument for determining the Frankfort-mandibular plane angle comprising a mandible contact plate including an upwardly disposed mandible contact flange along the forward portion of one side thereof, a transparent protractor disposed parallel and normal to the said flange and mandible contact plate respectively along the rearward portion of the same side thereof as said flange having its zero degree base line coincidental with the top of the said mandible contact plate, and a movable resilient protractor arm on the mandible contact plate side of the said protractor flexible in a direction normal thereto and torsionally manipulable to the contour ofa patients face.

DOUGLAS J. JAMIESON.

REFERENCES CITED The following referenIce-s are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 272,611 Abrahart Feb. 20, 1883 420,448 Gothard Feb. 4, 1890 566,948 Walker Sept. 1, 1896 765,837 Hirsch July 26, 1904 1,277,860 Civitts Sept. 3, 1918 1,412,162 Browning Apr. 11, 1922. 1,852,277 Wheeler Apr. 5, 1932 

